[unreadable] The overarching aim of the present NRSA proposal is to delineate empirical linkages between the cognitive risk factor for panic disorder (PD), termed anxiety sensitivity (AS; fear of anxiety), and acute nicotine withdrawal symptoms in order to better understand the etiology of panic vulnerability processes. This proposal links theory and research on cognitive vulnerability for PD with smoking research on acute nicotine withdrawal to test the hypothesis that hypersensitivity to interoceptive cues (i.e., AS) moderates the role of nicotine withdrawal in relation to panic-relevant responding to a carbon dioxide-enriched air (CO2) challenge among daily smokers. The specific aims of the present study are thus to test whether AS will moderate the relation between pre-challenge nicotine withdrawal and responding to a CO2 procedure (controlling for negative affectivity, anticipatory anxiety, cigarettes per day, and gender), as indexed by: (1) level of anxiety focused on bodily sensations and intensity of panic attack symptoms; (2) level of expired pCO2 and skin conductance reactivity; and (3) greater levels of behavioral avoidance of a future challenge. [unreadable] [unreadable] [unreadable] [unreadable] [unreadable]